Accelerated hole transfer by double-layered metallophthalocyanine thin film for effective electroluminescence

Abstract

An electroluminescent device was constructed using tris(8-hydroxyquinoline)aluminum as an emitting layer and metallophthalocyanine as a hole-transfer layer. When the metallophthalocyanine layer is sufficiently thin, the device shows a brightness of more than 1000 cd m−2. The device using double hole-transfer layers of two kinds of metallophthalocyanine exhibits a higher brightness than that using a single hole-transfer layer of the corresponding metallophthalocyanine. This phenomenon is well explained by the accelerated hole transfer in the double layer due to the construction of a “sequential potential field.”